One conventional example of a driver's seat of an agricultural and construction work vehicle is disclosed in Japanese Unexamined Patent Application Publication No. 2004-142559 (referred to as JP 2004-142559 hereinafter) which includes a drain hole (element 27b) for avoiding accumulation of rain water in a seating section of the driver's seat in outside work (see paragraph 0028 of the publication; FIGS. 2 to 4).
Another example is disclosed in Japanese Unexamined Patent Application Publication No. 9-123806 (referred to as JP 9-123806 hereinafter) which includes a seating section having a pair of right and left longitudinal guide grooves (element 32), and a transverse guide groove (element 31) communicating with the longitudinal guide grooves in a central portion of the seating section. The longitudinal guide grooves have rear ends communicating with guide grooves formed in a seatback section to form drain holes (element 36) in a boundary between the seatback section and the seating section (see paragraph 0015 of the publication; FIGS. 1 to 4).